Semiconductor relay device

Abstract

A semiconductor relay device includes a conversion circuit configured to receive an input signal from outside and pass a first current to a first node based on the input signal. A zener diode has an anode coupled to a second node and a cathode coupled to the first node. A resistor is coupled between the second node and a third node. A number n of diodes are serially coupled. A thyristor has an anode coupled to the first node, a cathode coupled to the second node, and a control terminal coupled to the third node. A transistor has a gate coupled to the first node. An anode of a diode at a first end of the n diodes is coupled to the first node, and a cathode of a diode at a second end of the n diodes is coupled to a third node.

The invention claimed is: 
     
         1 . A semiconductor relay device comprising:
 a conversion circuit configured to receive an input signal from outside, and pass a first current to a first node based on the input signal;   an overheat protection circuit provided between the first node and a second node and configured to short the first node to the second node while a temperature in the semiconductor relay device is higher than a predetermined temperature; and   a transistor having a gate coupled to the first node, wherein   the overheat protection circuit includes:   a zener diode having an anode coupled to the second node and a cathode coupled to the first node;   a resistor coupled between the second node and a third node;   a number n of diodes that are serially coupled, wherein an anode of a diode at a first end of the n diodes is coupled to the first node, and a cathode of a diode at a second end of the n diodes is coupled to the third node, where n is a natural number larger than or equal to 2; and   a thyristor having an anode coupled to the first node, a cathode coupled to the second node, and a control terminal coupled to the third node.   
     
     
         2 . The semiconductor relay device according to  claim 1 , further comprising a transmission circuit configured to output the input signal, wherein:
 the transmission circuit is a light emitting diode, and   the conversion circuit includes a photodiode.   
     
     
         3 . The semiconductor relay device according to  claim 1 , further comprising a transmission circuit configured to output the input signal, wherein:
 the input signal is a magnetic signal generated from a coil included in the transmission circuit, and   the conversion circuit includes a coil detecting the input signal.   
     
     
         4 . The semiconductor relay device according to  claim 1 , further comprising a transmission circuit configured to output the input signal, wherein:
 the transmission circuit connected to the conversion circuit via a capacitor, and   the input signal is an electric signal generated from the transmission circuit and transmitted to the conversion circuit via the capacitor.